The user must be unique on the server or unique on the workspace?

Hi Survey Solutions team,

I am using SuSo in the version 21.01 on a local installation and I would like to know if the user should be unique in the server o unique in the workspace?
Can someone explain the fourth point to me?

Thanks for explaining this new SuSo feature to me.

On the server: if Kevin is registered as an interviewer in workspace1, there can’t be another user Kevin anywhere else (in any other workspace) not even in a different role.

Thank you very much @sergiy .